The present invention is related to devices for translating rotational motion to linear motion using a lead screw with a drive nut threadably connected to the lead screw and more particularly to a device for isolating the eccentricities of the lead screw from the linear motion of a device driven off of the drive nut. A patent of interest for its showing of the state of the art is U.S. Pat. No. 3,977,262, entitled "Drive Mechanism For A Carriage" by J. E. Randolph, wherein there is disclosed a nut that is mounted on a lead screw and is constrained from rotational movement, and a mounting assembly which couples the nut to a linearly moveable carriage. The drive nut is loosely coupled to the mounting assembly so that it may be skewed by the eccentricities of the lead screw without binding on the lead screw. A spring is used to urge the nut against the mounting assembly to dampen bounce forces.
Another patent of interest is U.S. Pat. No. 4,530,251, entitled "Apparatus For Transmitting Motion To Work-Supporting Tables of Machine Tools And The Like", by K. Henle, wherein a non-rotating nut assembly is driven by a lead screw and is connected to a movable work carriage by a pair of links that are pivotly mounted, at one end, to the nut assembly, and at the other end to the movable work carriage to isolate flexures of the lead screw from the movable work carriage.
Yet another patent of interest is U.S. Pat. No. 4,597,303, entitled "Drivably Connecting Construction In Measuring Instrument" by T. Nakaya, wherein there is disclosed a non-rotating nut that is driven by a lead screw with the nut loosely coupled to a movable main member by a plurality of regularly spaced ball bearings such that the nut is provided with limited movement perpendicular to the long axis of the lead screw while being rigidly constrained to the movable main member along the long axis of the lead screw.
The accuracy requirements for a system which records information onto microfilm aperture cards, in the form of lines of data, is extremely high. Each line must be equally spaced otherwise the distortion will be clearly evident when the microfilm is viewed through a viewer, which, for example, magnifies the viewed area by a factor of 30 to 1.
When high resolution dot printing is used to create images, there are six thousand scans per inch with six thousand dots possible along each scan line. Accuracy of the spacing of these lines is therefore extremely important. The present invention provides that necessary degree of accuracy.